1. Field of Invention
The invention relates to a drive apparatus having an engine and an electric motor and, more particularly, to an engine start control for the apparatus.
2. Description of Related Art
In a hybrid drive apparatus using an engine (or a combustion engine) and an electric motor together as its power source, when the engine fuel-cut is restarted while the vehicle is running, the cranking load of the engine affects the motor torque to be outputted to a wheel. Thus, a relatively high cranking shock is caused by the fluctuation in the drive torque. As a technique of the related art for reducing this cranking shock, therefore, there is a technique disclosed in Japanese Patent Laid-Open No. 82332/1998. In this related art technique, there is adopted a method for reducing the cranking torque of the engine. When the engine is motored and started by a motor coupled mechanically to the crank-shaft through a damper, the opening/closing timings of an intake valve of the engine are delayed to reduce the effective compression ratio of the engine so that the engine may be rotationally driven smoothly to reduce the amplitude of the torsional vibration of the crank-shaft and to quickly pass the rotational range in which the resonant phenomenon occurs.
Here, the crank angle at the engine stop time does not fall at an identical position but always disperses. Depending upon this difference in the engine stop position, the rise in the engine speed may be delayed at the initial stage of the engine start and may fail to quickly pass the rotational range of the resonance phenomenon. Even if the cranking torque is effectively reduced, moreover, the torque fluctuation to be transmitted to the wheel at the engine starting time is different due to the difference in the engine stop position so that the inexpensive feedforward control for correcting the torque fluctuation cannot be made on the basis of the simple correction waveform data. In order to absorb this torque fluctuation effectively, it is necessary to always add different torque corrections. This torque correction requires a complicated feedback control.